Heart failure is one of the most widespread and devastating cardiac afflictions, currently affecting approximately 15 million people worldwide, including over 5 million in the United States. In the U.S., approximately 450,000 new patients are diagnosed with heart failure each year and the majority dies within five years of diagnosis. One factor that contributes to heart failure is asynchronous activation of the ventricles such that the mechanical contraction is not coordinated effectively thus compromising cardiac function. As a result, the pumping ability of the heart is diminished and the patient experiences shortness of breath, fatigue, swelling, and other debilitating symptoms. The weakened heart is also susceptible to potentially lethal ventricular tachyarrhythmias. A decrease in cardiac function can result in a progression of heart failure. In many cases, pacing control parameters of the pacemaker or implantable cardioverter defibrillator (ICD) can be adjusted to help improve cardiac function and reduce the degree of heart failure effectively reducing symptoms and improving the quality of life.
One particularly promising technique for reducing the risk of heart failure is cardiac resynchronization therapy (CRT), which seeks to normalize asynchronous cardiac electrical activation and the resultant asynchronous contractions by delivering synchronized pacing stimulus to both ventricles using pacemakers or implantable cardioverter defibrillators (ICDs) equipped with biventricular pacing capability. The stimulus is synchronized so as to help to improve overall cardiac function. This may have the additional beneficial effect of reducing the susceptibility to life-threatening tachyarrhythmias.
While CRT is promising and has helped many patients, some CRT patients have benefited less than others. This has caused the medical community to focus more intensely on the initial question, given a particular patient, is CRT appropriate? As a consequence, various tests and decision processes have emerged to aid in determining whether a patient will respond to CRT. Patients that are likely to respond or do respond have been referred to as “responders”. However, the class of actual responders has been confined by regulatory, device and procedural concerns or capabilities. For example, limitations exist as to actual locations considered or approved for positioning a left ventricular stimulation electrode. Thus, an appropriate inquiry is whether the likelihood of a patient responding to CRT depends on the selected stimulation site or sites?
As described herein, surface ECG information is used, optionally in conjunction with other information, to determine one or more stimulation sites for CRT or stimulation based cardiac therapy. Such techniques can help assess a patient's likelihood of responding to therapy prior to implantation of a cardiac therapy device.